The aim of this research was to investigate the antimicrobial activity of silver nanoparticles (AgNPs) biosynthesized by Pseudopediastrum boryanum (Turpin) E. on several human pathogen microorganisms. AgNPs were isolated from P. boryanum. The biosynthesis of AgNPs was carried out using a UV-visible spectrophotometer and FTIR spectroscopy analysis. The antimicrobial activity of AgNPs was evaluated against various pathogen microorganisms using the well diffusion method, and MIC was estimated by qualitative experimentation by microbroth dilution method. The antimicrobial activities of AgNPs at three different concentrations (1 mM, 2 mM and 3 mM) were measured using the diameter of the inhibition zone (DIZ) of the pathogen microorganisms. AgNPs demonstrated various antimicrobial effects on pathogen microorganisms at different concentrations. The highest antimicrobial activity was determined in Proteus vulgaris [DIZ = 30 +/- 0.2 mm (2 and 3 mM)], followed by Candida parapsilosis (M006) [DIZ = 25 +/- 0.1 mm (3 mM)], followed by Pseudomonas aeruginosa [DIZ = 20 mm (2 and 3 mM)] and Candida parapsilosis (M006) [DIZ = 20 mm (1 and 2 mM)]. The lowest antibacterial effects of AgNPs were observed on Aeromonas hydrophila [DIZ = 5 +/- 0.1 mm (3 mM)], Staphylococcus epidermidis [DIZ = 5 +/- 0.1 mm (1 mM)], Candida parapsilosis [DIZ = 5 +/- 0.1 mm (2 mM)] and Candida albicans [DIZ = 5 +/- 0.1 mm (3 mM)]. Gram-negative bacteria Proteus mirabilis, Enterobacter aerogenes, Salmonella typhimurium, Shigella dysenteriae, Escherichia coli and Serratia marcescens and Gram-positive bacteria Listeria monocytogenes and Enterococcus faecalis exhibited no zone of inhibition. Our results confirm that AgNPs biosynthesized from P. boryanum may be used as an effective antimicrobial agent against human pathogens.